Spline teeth



Oct. 28, 1930. I D D UNWOODlE 1,779,805

SPLINE TEETH Filed Maron 1, 192; 2 sheets-sheet 2 I N VEN TOR DHV/0Dl//VWOOD/E p Patented Oct. 28, 1930 DA nUNwoonrE, or DAYTON, omo

SPLINE TEETE Application led March 1, 1923. Serial No. 622,109. f

This invention relates to a new form of spline for coupling together ashaft and a driven member such as used in automobile transmissions ofthe selective type and in various other mechanisms where splines may beused and the object of the invention is to provide a spline which may bemore easily and accurately made and constructedV and which will bestronger than those heretofore known. Further objects will be more fullyset forth in the attached specification and claims:

In the drawings: Fig. l is a plan view of a shaft showing th splineteeth.

Fig. 2 is an end elevation of the -inside spline member. Fig. 3 is anenlarged transverse section of Fi 2 showing parts of both splinemembers. Fig. 4 is an end view of a modification of 20 my invention;

Fig. 5 is a side elevational view of Fig. 4 showing the slight taperedgroove grossly exaggerated; and

Fig. 6 is a cross-sectional' view taken on the line 6-6 of Fig. 4showing the outside member, having normally an inner bore of constantdiameter, in section and pressed fitted onto the inside member.

A satisfactory spline fitting or shaft has not been available. Splined`shafts were defective because a erfect centering of the shaft and hubma e by the known methods was practically impossible. The S. A. E.spline which is formed by cutting slots on a shaft leaving splines withstraight sides parallel to the radial lines from the center has severaldisadvantages. It is difficult to obtain a good t between this type ofspline shaft and hub. The accuracy of this method is dependent to agreat extent upon the accuracy of three bearing surfaces. Itis ywellknown that the form of cutter used in cutting S. A. E. splines,especially when of the concentric relievedv type cannot be groundsatisfactorily after hardening. It is furthermore difficult to obtain anaccurate relationship of the three cutting faces and keep them true.-The slightest amount of wearvon any one of the cuttin faces of this typeof cutter will effect the re ationship of the groove andY spline. Itsaccuracy cannot, therefore, be as sured; hence this process of cuttingsplines is not under absolute control.-

With my typeof spline, however, a good fit between the shaft and hub issimply and accurately obtained. Since the type of cutter used in cuttingthe grooves to form my spline necessitatesrbut two cutting faces thatare easily held in constant relationship, it is comparatively moreeasily and satisfactorily ground after hardening and slight wear on thecutting faces would necessitate but a slightl deeper cut, and hence haslittle, if any, e ect on the relationship of the splines and grooves.This process of cutting splines being under the Vcontrol of theoperator, greater accuracy than was heretofore possible is obtained withthe result that better fits and inter-changeability of parts is madepossible. yIt is well known that with the S. A. Er. t pe of spline halfthe splines are actually dBi-iving, whereas in my device all the splinescarry their share of the drivin load and due to the fact that thesedriving aces are angularly disposed, there is a tendency of the hubalways to remain concentric with the shaft when under load. yConcentricity of the S. A. E. spline under load is practicallyimpossible.

It is furthermore well .known that in any spline shaft the. distancebetween the splines must be maintained rigidly in order to preventloosenessV between the shaft and hub members which have a sliding fit.As the distance between the spline in the S. A. E. type when using theconcentric relieved type of cutter is a function of the depth of cutAand `as the bottom of the grooves between the splines must beaccurately shaped and located with respect to vthe center of the shaftin order to obtain accurate centering of the shaft and hub members, itwill readily be seen that any discrepancyin the depth of cut will haveacorresponding effect upon the fit and centering between the members.Whereas, with my spline a slight discrepancy in the depth of cut has no`effect upon the vcentering due to the self-centering characteristics ofthe angular driving faces.

Referring to the drawings in which similar 10 mY i reference numeralsindicate corresponding parts, 1 is a shaft having at one end thereof aportion of constant diameter provided with Spline teeth 2, which engagethe corresponding teeth 3 of the hub or outside member 4 which is to becoupled to the shaft 1. The

Y respectively of the inside member, the ineluded angle of the teethbeing the same as the included angle of the grooves on the shaft. Theteeth 2 are formed as shown with flat sides 5 engaging with the flatsides 6 of the outside teeth.

The spline shaft and outside member shown in the drawings havetwenty-four teeth each, regardless of the diameter of the shaft, and theangle between the sides 5, 5 of the teeth is 45. The angle between thesides 6, G of the teeth 3 is 60. Both the teeth 2 and 3 are shown asformed with arcuate roots 7 and 8, and are cut and arranged as to leavetheI vertices of the projections fiat in order to insure the two partsengaging at or 011 the sides of the groovesand projections only.

It is to be understood that by having 24 teeth, there will be one toothfor every 15 degrees around the circumference and by using straightsided cutters of 60 and 45 for cutting the teeth, the work may be moreeasily set up preparatory to cutting the teeth. It will be seen byreferring to Fig. 3 by inspection, that since the included anglesubtended by adjacent teeth is 15, the angle between the sides of atooth of the inner mem` ber added to the angle subtended by the saidadjacent teeth of the inner member will equal the an le included betweenthe sides of the teeth o the outside member. This may quite readily beproved geometrically and is readily obvious.'

When it is desired to have a spline made regardless of the diameter orlength of the spline, the mechanic merely takes up an ordinary 60cutting tool which is a standard tool for milling, grinding, or shapingmachines,

and this standard tool is used for cutting the teeth on the insidemember, also for cutting a broach for the outside member. The cuttersmay be easily sharpened or reground and may be sharpened as often asdesired without affecting their serviceability. After being resharpened,the cutters may be easily inspected and checked, the even 45 Aand 60angles, and the straight sides of the cutters rendering this aneasymatter. Furthermore member 4 being of constant diameter. The

grooves between the teeth 5 of the inside member l are cut deeper at oneend of the spline than at the other end by gradual withdrawal of thecutter or by raising the center of one end of the material being cut afew ten thousandths of an inch toward the cutter. It will therefore beapparent that one' thousandth of an inch difference in the centers ofthe cutter and shaft from the beginning to the end of the cutting strokewill produce one thousandth of an inch clearance or taper at the taperedend due to the even 60 angle of the groove, thus making the calculationas well as the assembly casier. The pitch of this taper formed by havingthe bottoms of the grooves at a slight angle from the horizontal variesfrom a fraction of a thousandth part of an inch to several thousandthspredetermined by conditions and nature of the work together withmaterials used in the length of the splined part of the shaft. Ingeneral the pitch of the taper of the groove is substantially the sameas, or smaller than thel degree of extension of the hub member whenstretched to its elastic limit. The pitch at the inner end of thetapered groove is the increase in the distance from the axis of theshaft at that point over the distance from the shaft axis to the taperedsurface at the end of the shaft. Since the outside member .is providedwith a straight broached bore of constant diameter, the inside memberbeing of constant diameter, but provided with a se# ries of taperedgrooves, a pressed t in the power transmitting sides of the teeth willbe obtained when the outside member is forced onto the inside member.One operation, therefore, may eut or machine the tooth and the taper.Press fits may be obtained with my spline in the usual and Well knownmanner. When the spline partsy are assembled in the case of a press fitobtained as above described or in the usual way and in the case of asliding it where the depth of the grooves of the shaft and outsidemembers is uniform throughout the length of the splined portion, theslides or faces of the teeth are in engagement practically their entirearea.

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If one of the spline parts is of softer metal or the 45 and 60 angles.In this way it is very easy to obtain a fatter tooth for the softermetal where the added strength is desired. This feature is quite easilyand accurately obtained in a spline constructed as set a gear, wheel,propeller, or any one of various other devices whose center has tocoincide accurately with the central axis with the shaft on which it iscarried and that the fit between the' members will be a sliding fit or apress lit, depending uponwhether the outside member is intended inoperation to slide upon the shaft or whether the member is mounted at afixed point in the length of then 'e splined portion of the shaft.

While it is desirable to have twenty-four teeth on the spline memberswith the included angles of the grooves and teeth on the shaft member 60and 45 respectively, this relationship in carrying out my invention isnot absolutely necessary. My invention contemplates broadly anymodifeation of a multiple spline fitting in which the angles of thegrooves are 60 for any predetermined number of projections, theprojections having flat angularly disposed sides lying in planesparallel or substantially parallel to the axis of the fitting; thegrooves having iiat or arcuate bottoms lying parallel or substantiallyparallel to the axis of the shaft.

I am aware that my invention is capable of various modifications and Ido not desire to be limited to the invention illustrated in the drawingand described in the specification, except as deinedby the appendedclaims.

I claim:

l. In a device of the class described, a shaft provided with acylindrical portion, an outside member provided with a cylindrical bore,receivingsaidshaft twenty-four intermeshing teeth on both saidcylindrical portion of the shaft and the interior of said member forconnecting the same,\all of said teeth having flat sides, the includedangle between the sides of each tooth on the shaft being and theincluded angle between the sides of o. each tooth onV said member being2. `In a straight spline coupling, an inside and an outside toothedmember, the outside end of the spline than at the other, whereby whenthe outside member is mounted on the inside member a press fit isprovided for the members. i

3. In astraight spline coupling, an; inside and an outside member, theoutside member having a bore receiving the inside member 24 intermeshingteeth on each of said members for connecting the same, all of saidteethv having iat angularly disposed sides, the included angle betweenthe sides of each tooth on the inside member being exactly 45 and theincluded angle between the sides of each tooth on the outside memberbeing exactly 60, the depth of the tooth forming grooves of only one ofsaid members being slightly greater at one end of the spline tha'n atthe other, whereby when the outside member is fixed tothe inside membera press fit is provided for the members. V

4. In a straight spline coupling, inside and outside toothed members,said outside member receiving said inside member said teeth havinginterengaging iiat sides and each tooth being shaped substantially intheform of a V, the depth of the tooth forming grooves of said insidemember being slightly greater at the outer end of the spline than at theinner end, the grooves in the outside member being parallel to the axisthereof, whereby when the outside member is splined onto the insidemember a press fit is provided for the members. y

5. In a device of the class described, a shaft member of constantdiameter, and an outside member having a bore and receiving said shaftmember, each member having a series of grooves and projections forconnecting the same, all of said projections having flat sides angularlydisposed with respect to each other,

the angle of each groove` in the one member being 60 for anypredetermined number of projections on said member and the angle ofveach proj ection in the other member being 60 6. A shaft with V-shapedintegral s lines having flat side faces forming V-s aped grooves, theincluded angles of the splines and grooves being 45 degrees and 60degrees respectively.

7. A multiple splined iitting of the class described having a straightportion of constant diameter, said portion being provided with aplurality of V-shaped projections and V-shaped grooves, adapted to meshwith complementary grooves and projections, respectively of an outsidemember, the included angle of the grooves being 60Vdegrees for apredetermined number of projections. j

8.v A shaft having a straight portion provided with integral projectingsplines, said s lines being provided with non-parallel side aces andwith angular grooves between them, the angle of the grooves beingsubstantially 60 degrees.

In testimony whereof I aiix my signature.

' DAVID DUNWOQDIE.

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